Implement NvVarsFileLib to save and restore non-volatile variables using a file.

This library provides an interface where variables can be saved and restored
using a file in a file system accessible to the firmware.  It is expected
that a platform BDS library will use this library.  The platform BDS
implementation can decide which devices to connect and then to attempt to use
for saving and restoring NV variables.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9272 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/Library/NvVarsFileLib/NvVarsFileLib.c

@@ -0,0 +1,53 @@
+/** @file
+  Save Non-Volatile Variables to a file system.
+
+  Copyright (c) 2009, Intel Corporation. <BR>
+  All rights reserved. This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#include "NvVarsFileLib.h"
+#include <Library/DebugLib.h>
+#include <Library/NvVarsFileLib.h>
+
+
+/**
+  Attempts to connect the NvVarsFileLib to the specified file system.
+
+  @param[in]  FsHandle - Handle for a gEfiSimpleFileSystemProtocolGuid instance
+
+  @return     The EFI_STATUS while attempting to connect the NvVarsFileLib
+              to the file system instance.
+  @retval     EFI_SUCCESS - The given file system was connected successfully
+
+**/
+EFI_STATUS
+EFIAPI
+ConnectNvVarsToFileSystem (
+  IN EFI_HANDLE    FsHandle
+  )
+{
+  EFI_STATUS Status;
+
+  //
+  // We might fail to load the variable, since the file system initially
+  // will not have the NvVars file.
+  //
+  LoadNvVarsFromFs (FsHandle);
+
+  //
+  // We must be able to save the variables successfully to the file system
+  // to have connected successfully.
+  //
+  Status = SaveNvVarsToFs (FsHandle);
+
+  return Status;
+}
+
+